SEQUENCE OF OPERATION
Sequence of Operation- Double Element, Non-Simultaneous Operation, 3 Phase.
Line voltage is appliedacross terminals L1
&L3 of upper thermostat. Likewise, Line
voltage is appliedto terminal L3 of lower
thermostat. ECO in both upper & lower
thermostat is closed, so thereis voltage at
terminal L4 of both thermostats and to one
side of both upper &lower elements.
Tank is cold thereforeboth thermostats
are closedat terminal T2 (calling for heat).
The circuitis complete through the upper
thermostat only allowing current to flow
through the upper element.
1
2
When the upper thermostatis satisfied, it
opens at terminal T2 interrupting current
flow through upper element,and closes at
terminal T4 allowing voltage to pass to
terminal L1 of lower thermostat.This
completes the circuit through the lower
thermostat allowing current flow through
lower element.
When the lower thermostat is satisfied, it
opens at terminal T2 interrupting the
current flow through the lower element. The
system is now in stand-by mode waiting for
the next call forheat.
3
4
The lower thermostat/element combination
will generally cycle on and off moreoften
then the upper. In some cases, such as a
cold tank or in high demand periods, the
upper thermostat will call forheat (opening
at terminal T4 and closing at terminal T2)
prior to the lower thermostatbeing satisfied.
This will interrupt currentflow through the
lower thermostat and element and allow
current to flow through the upper element
only. When the upper thermostat is
satisfied, it resumes operation as described
in sequence #3 above.
5
ECO
Closed
1 2
Thermostat closed
at terminal T2
Thermostat closed
at terminal T2
3
Thermostat closed
at terminalT4
Thermostat closed
at terminal T2
4
Thermostat closed
at terminal T4
Thermostat open
at terminalT2
5
Thermostat closed
at terminal T2
Thermostat closed
at terminalT2
ECO
Closed
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